Nucleic acid sequencing such as DNA sequencing is the process of determining the precise order of nucleotides within a DNA molecule. It includes any method or technology that is used to determine the order of the four bases—adenine, guanine, cytosine, and thymine—in a strand of DNA. The advent of rapid DNA sequencing methods has greatly accelerated biological and medical research and discovery. Knowledge of DNA sequences has become indispensable for basic biological research, and in numerous applied fields such as diagnostic, biotechnology, forensic biology, and biological systematics. The rapid speed of sequencing attained with modern DNA sequencing technology has been instrumental in the sequencing of complete DNA sequences, or genomes of numerous types and species of life, including the human genome and other complete DNA sequences of many animal, plant, and microbial species.
The first DNA sequences were obtained in the early 1970s by academic researchers using laborious methods based on two-dimensional chromatography. Following the development of fluorescence-based sequencing methods with automated analysis, DNA sequencing has become easier and orders of magnitude faster.
However, many sequencing methods rely on ensemble measurements and cannot be carried out on a single DNA molecule basis. Furthermore, most currently used sequencing methods entail a labeling of the nucleotides which are incorporated into the template DNA strand, which leads to certain disadvantageous during the sample preparation and the measurement itself. Further, the need for labeled dNTPs used for sequencing increases the costs. Moreover, a part of the state of the art sequencing methods make use of pyro-phosphate for the generation of a detection signal, which however is relatively insensitive.